Central England Temperature (part 7)
A sideways look at the longest instrumental record of temperature in the world
In part 6 of this series I wore my best skullcap and introduced readers to new ways of looking the relationship between atmospheric CO2 and central England mean annual temperature for the period 1659 - 2021. We discovered a few facts that pulled the rug right from under the notion that man-made CO2 is driving current era warming. It most certainly ain’t, and there is a jolly good reason it ain’t and that is encapsulated in the word ‘saturation’: at 410ppm we are at a point where more CO2 isn’t going to make the slightest bit of difference to the greenhouse effect. Not only that but there are signs the Earth is entering another cool phase. But I digress… let us get backing to thinking about the world’s longest time series for land surface temperature (HADCET).
What A Whopper!
At 363 annual means long we are looking at a whopper. Not just a whopper with whose beauty is skin deep, but a deeply fabulous thing, it being witness to a truck load of social and political history that started before sliced bread was invented. Whilst sipping a steaming hot mug of red bush tea this morning I had the notion of running the series through spectral analysis just to see what I could see.
Spectral analysis is a rather clever technique that allows us to detect periodicity within a time dependent signal. If we considered monthly temperature data we’d pick up a signal with a frequency component of 0.083 which corresponds to the annual cycle of 12 months (1/0.083 = 12). So let’s have a look at a periodogram of frequencies for the central England mean annual temperature record:
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